1. Technical Field
The present invention relates to an apparatus and method for collecting impurities on a semiconductor wafer and, more particularly, to an automated apparatus and method for scanning a semiconductor wafer to collect metallic impurities on the semiconductor wafer.
2. Description of Related Art
As semiconductor devices become highly integrated, various types of impurities are generated during a semiconductor manufacturing process that settle on a semiconductor wafer. These impurities cause deterioration in the performance of semiconductor devices, as well as lower yields in the manufacturing of semiconductor devices. There is a need therefore for improved methods and devices for removing impurities on semiconductor devices.
One conventional method of analyzing impurities on a semiconductor wafer is as follows. A manufactured semiconductor wafer is selected and then scanned to collect an impurity sample. The impurity sample is then analyzed using an analysis technique such as an atomic absorption spectroscopy (AAS), an induction coupled plasma (ICP) mass spectroscopy, and a total x-ray fluorescent analyzer.
To properly collect the impurities on the semiconductor wafer, a silicon oxide layer that is coated on the surface of the semiconductor wafer is first decomposed using, for example, a VPD (vapor phase decomposition) apparatus.
A conventional VPD apparatus comprises a process chamber, a loading plate for loading the semiconductor wafer into the process chamber, and a container containing a hydrofluoric acid (HF) that is used to decompose a silicon oxide layer of the surface of the semiconductor wafer. When the semiconductor wafer is transferred to the loading plate in the process chamber, the semiconductor wafer rests on the loading plate for a predetermined time period, and the silicon oxide layer is decomposed from the surface of the semiconductor wafer by HF vapors generated in the container. Afterwards, the semiconductor wafer is taken out of the process chamber. A scanning solution is dropped onto the semiconductor wafer and is scanned, thereby collecting the impurity sample manually. The collected impurity sample is analyzed using a technique such as the AAS, the ICP-mass spectroscopy, and the total x-ray fluorescent analyzer.
One disadvantage associated with the above-described conventional method for collecting metallic impurities on the semiconductor wafer is that the scanning process is manually performed and, consequently, the reliability of analyzed data depends on the skill of the person who performs the impurity collection. Another disadvantage is that the semiconductor wafer is scanned in the air and, consequently, alien substances in the air can contaminate the impurity sample. Therefore, it is difficult to precisely analyze the impurity sample.